The invention relates, in general, to gas-cooled dynamoelectric machines; and, in particular, to an apparatus in combination with a gas-cooled dynamoelectric machine for collecting thermal decomposition products which may occur in the machine gas coolant if there is localized overheating of certain dynamoelectric machine parts.
In U.S. Pat. No. 3,428,838 to Carson et al issued Feb. 18, 1969, a wear detector apparatus comprising a mechanical filter is used in combination with a gas-cooled dynamoelectric machine to determine excessive wear of winding insulations caused by machine vibrations and thermal cycling. In other words, an external monitor is used to determine an internal operating condition of the dynamoelectric machine using the machine gas coolant as a carrier medium. This device is very useful in giving an early warning of a possible detrimental condition within the dynamoelectric machine prior to a more serious condition such as short circuit.
Another type of device in U.S. Pat. No. 3,427,880 to Grobel et al issued Feb. 18, 1969 takes advantage of the fact that certain types of machine coatings will emit thermal decomposition products when machine parts, thus coated, become overheated. The coatings are organic materials and the thermal decomposition products therefrom are pyrolysates. The patented invention employs an ion chamber detector of the type shown in U.S. Pat. No. 3,573,460 to Skala issued Apr. 6, 1971 in combination with a gas-cooled dynamoelectric machine. The ion chamber detector senses the presence of pyrolysates and sounds an alarm.
Localized overheating in a large gas-cooled dynamoelectric machine is a rare occurrence; however, a stator core damaged by overheating may lead to extensive machine outage and costly repairs. Hence, the invention described in U.S. Pat. No. 3,427,880 for detecting machine overheating makes an important contribution to the art by making possible an early warning of machine overheating. Because of the particular identifiable characteristics of pyrolysate products it is also possible to determine the location of the overheating, as pointed out in U.S. Pat. No. 3,807,218 to Carson et al issued Apr. 30, 1974. In that patent, a sampling device is used to collect pyrolysates whereupon the sample is removed from the sampling device for qualitative analysis. The sampling device comprises an absorbent sampling media such as silica gel primarily for removing particulate pyrolysates from the machine gas coolant. According to one aspect of the present invention, it has been found that the collection and analysis steps could be enhanced by the use of several different kinds of sampling media.
The present invention is an apparatus for collecting both gaseous and particulate products from the gas coolant of a gas-cooled dynamoelectric machine. The apparatus includes a collector which employs several different kinds of sampling media. The sampling media are contained in separate cartridges within the collector and are easily removable therefrom for analysis. The apparatus also includes a piping circuit which is so arranged as to permit an initial inlet purge, a collection step and an after-collection collector purge. Moreover, an electrical circuit is provided for controlling both the inlet purge and the collection step in timed sequence. Finally, the entire apparatus is packaged in a cabinet for modular assembly to a dynamoelectric machine.
It is therefore one object of the present invention to provide an improved apparatus for collecting thermal decomposition products from the gas coolant of a gas-cooled dynamoelectric machine.
It is another object of the present invention to provide a collector apparatus which optimizes the collection of both gaseous and particulate thermal decomposition products.
It is a further object of the present invention to provide a self-contained collector apparatus which includes purge cycles and wherein the collected samples are readily removable therefrom.
These objects and advantages of the present invention will become apparent from the following detailed description of the invention when taken in connection with the appended drawings.